In complex systems comprised of many components, or sub-systems, it may be desirable to assess the health of each of the individual components, or sub-systems, comprising the system in order to determine the health of the overall system. In such a system, it may be difficult to isolate a system failure due to the complex interaction amongst the components comprising the system. It is also desirable to be able to predict when a component's performance has degraded to the point where a maintenance action is beneficial so that the action can be performed prior to a system performance degradation. Typically, each component's health is assessed by a built-in-test (“BIT”), but in such a system all the individual components may not be accessible for BIT.